U.S. patent number 4,005,763 [Application Number 05/559,660] was granted by the patent office on 1977-02-01 for lubricating means for gas-operated cylinders.
Invention is credited to Bernard J. Wallis.
United States Patent |
4,005,763 |
Wallis |
February 1, 1977 |
Lubricating means for gas-operated cylinders
Abstract
Lubricating means for a piston-cylinder unit operated by
non-lubricated gas under pressure comprising a passageway in the
piston-cylinder unit extending from the surrounding atmosphere to
the cylinder chamber on the side of the piston opposite that to
which the pressurized gas is directed. A lubricant-impregnated
material is located in the passageway so that, as air flows into
said chamber in response to movement of the piston in the cylinder,
the lubricant is entrained in the air and is carried into the
cylinder to lubricate the contacting surfaces of the piston and
cylinder. In addition, a lubricant-impregnated wick is arranged
within the piston rod and contacts the conventionally used
lubricant-impregnated felt ring on the piston to prolong the supply
of lubricant to the ring.
Inventors: |
Wallis; Bernard J. (Dearborn,
MI) |
Family
ID: |
24234482 |
Appl.
No.: |
05/559,660 |
Filed: |
March 19, 1975 |
Current U.S.
Class: |
184/24; 184/55.2;
92/153; 267/119 |
Current CPC
Class: |
F16F
9/3278 (20130101); F16J 1/08 (20130101) |
Current International
Class: |
F16F
9/32 (20060101); F16J 1/08 (20060101); F16J
1/00 (20060101); F16N 001/00 () |
Field of
Search: |
;184/24,18,19,20,6.8,5,29,32,55A
;92/153,154,155,156,157,158,159,160,78 ;267/118,119 ;277/17,19 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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|
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317,263 |
|
Aug 1929 |
|
UK |
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215,668 |
|
Jun 1968 |
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SU |
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Primary Examiner: Apley; Richard J.
Assistant Examiner: Kramer; Arnold W.
Attorney, Agent or Firm: Barnes, Kisselle, Raisch &
Choate
Claims
I claim:
1. In combination a cylinder, a piston movable axially in the
cylinder and dividing the cylinder into a working chamber and an
idle chamber which vary inversely in size in accordance with
movement of the piston axially in the cylinder, means communicating
said working chamber with a source of pressurized gas and
permitting said gas to flow into and out of said working chamber,
passageway means establishing communication between the surrounding
atmosphere exteriorly of said cylinder and said idle chamber and
permitting the flow of air into and out of said idle chamber, and
air permeable means in at least one section of said passageway
means impregnated with a lubricant, said air permeable means being
disposed so that air flowing through said one section of said
passageway means into said idle chamber is directed into intimate
contact with said lubricant to entrain the lubricant in said air,
whereby said piston and the internal walls of said idle chamber are
lubricated by the lubricant entrained in the air flowing into said
idle chamber.
2. The combination called for in claim 1 wherein said passageway
means includes an inlet passageway in which said lubricant
impregnated means is disposed and an exhaust passageway for
exhausting air from said idle chamber back into the surrounding
atmosphere and means in said inlet passageway preventing flow of
air therein from said idle chamber to the surrounding
atmosphere.
3. The combination called for in claim 1 wherein said passageway
means comprises an inlet passageway and including orifice means
connecting said inlet passageway and said idle chamber to permit
the flow of air therethrough into said idle chamber in response to
a pressure differential in said passageway resulting from enlarging
of the idle chamber as the piston moves toward one end of the
cylinder and preventing flow of air out of said idle chamber
through said inlet passageway in response to contraction in the
size of the idle chamber.
4. The combination called for in claim 1 wherein said air permeable
means comprises a porous wick.
5. The combination called for in claim 4 wherein said wick is
impregnated with oil.
6. The combination called for in claim 1 wherein said passageway
means extends at least in part circumferentially around said
cylinder.
7. The combination called for in claim 6 including a plurality of
circumferentially spaced openings in the circumferentially
extending portion of said passageway means communicating with the
surrounding atmosphere exteriorly of said cylinder.
8. The combination called for in claim 7 wherein said air permeable
means extends throughout at least a major extent of the
circumferentially extending portion of the passageway means.
9. The combination called for in claim 8 wherein said air permeable
means has circumferentially spaced parted ends, one of said
openings registering with the space between said parted ends, said
space communicating directly with said idle chamber rather than
through said lubricant-impregnated means.
10. The combination called for in claim 1 including a piston rod
connected to said piston and extending axially through said idle
chamber, means defining a wall adjacent the end of the idle chamber
opposite the piston, said end wall having a bore therein, said
piston rod extending through said bore with a close fit whereby the
lubricant/air mixture in said idle chamber lubricates said piston
rod and bore.
11. The combination called for in claim 10 including a central bore
extending axially in said piston rod, a lubricant-impregnated
material in said bore, said piston having a lubricant-impregnated
ring extending circumferentially around the piston and engaging the
side wall of the cylinder, and means forming a radially extending
passageway establishing communication between said central bore and
said ring.
12. The combination called for in claim 11 including a
lubricant-impregnated material in said radially extending
passageway.
13. The combination called for in claim 1 including a
unidirectional valve in said one section of said passageway means
for admitting air to said idle chamber.
14. The combination called for in claim 13 including a second
unidirectional valve in another section of said passageway means
for permitting air to escape from said chamber in response to
contraction in size of the idle chamber as a result of axial
movement of said piston in said cylinder.
15. The combination called for in claim 13 wherein another section
of said passageway means comprises an exhaust passageway extending
from said idle chamber to the surrounding air, said exhaust
passageway being restricted in size relative to said one section of
said passageway means to minimize the flow of air into said idle
chamber through said exhaust passageway.
16. The combination called for in claim 1 including a piston rod
connected to said piston and extending axially through said idle
chamber and the adjacent end of the cylinder, an annular cap on
said end of the cylinder through which the piston rod extends, said
cap having a peripheral skirt which extends circumferentially
around and overhangs the outer periphery of said cylinder at said
one end thereof, said passageway means being defined at least in
part by said overhanging skirt.
17. The combination called for in claim 16 wherein said passageway
means extends circumferentially around the cylinder within the
axial extent of the overhanging skirt.
18. The combination called for in claim 17 wherein the
circumferentially extending portion of said passageway means
extends axially in a direction toward said end of the cylinder,
said passageway means then extending radially inwardly beyond the
inner periphery of the cylinder wall and then axially toward said
piston into said idle chamber.
19. The combination called for in claim 18 wherein said
lubricant-impregnated means is disposed in the circumferentially
extending portion of said passageway.
20. In a die assembly of the type which includes a support, a die
member movable toward and away from said support, and a fluid
spring extending between said die member and said support, said
fluid spring comprising a piston movable axially within a cylinder
and having a piston rod extending through an end wall of the
cylinder so that when a gas under sufficient pressure is directed
to the end of the cylinder opposite the rod end thereof the rod and
cylinder apply forces to the support and die member which tend to
move them relatively away from one another and when the force on
the die member is sufficient it overcomes the pressure in the end
of the cylinder opposite the rod end thereof and causes the piston
to move in a direction away from the rod end thereof and causes
said die member and support to move relatively toward one another,
the improvement which comprises, a passageway for admitting air
from the surrounding atmosphere into the rod end of the cylinder in
response to movement of the piston in a direction away from the rod
end of the cylinder, and lubricant-impregnated, air permeable means
in said passageway, said lubricant being of the type which is
adapted to be entrained in the air flowing into the rod end of the
cylinder through said passageway to thereby lubricate the piston,
the piston rod and the interior walls of the cylinder.
21. The combination called for in claim 20 including valve means in
said passageway for admitting air to the rod end of the cylinder in
response to movement of the piston axially in a direction away from
the rod end of the cylinder.
22. The combination called for in claim 21 including an exhaust
passageway extending from the rod end of the cylinder to the
surrounding atmosphere for discharging air from the rod end of the
cylinder when the piston moves axially in a direction toward the
rod end of the cylinder.
23. The combination called for in claim 22 including an annular cap
extending over the rod end of the cylinder and having an axially
extending skirt thereon which overhangs the outer periphery of the
cylinder, said passageway being defined at least in part by said
cap.
24. The combination called for in claim 23 wherein said passageway
extends circumferentially between the side wall of the cylinder and
the overhanging skirt of the cap.
25. The combination called for in claim 24 wherein said
lubricant-impregnated means is disposed within the
circumferentially extending portion of said passageway.
26. The combination called for in claim 25 wherein said passageway
communicates with the surrounding air through a plurality of
circumferentially spaced air inlet openings around said cap.
27. The combination called for in claim 26 wherein said air inlet
openings are radially oriented.
28. The combination called for in claim 27 wherein said skirt is
provided with a plurality of axially spaced, radially outwardly
extending fins thereon, said air inlet openings being located
between a pair of adjacent fins.
29. The combination called for in claim 20 wherein the end of the
cylinder opposite the rod end thereof is connected with a reservoir
charged with gas under pressure.
30. The combination called for in claim 20 wherein said piston rod
has an axially extending passageway therein, said piston having a
lubricant-impregnated ring thereon contacting the wall of the
cylinder, a passageway in said piston extending radially outwardly
from said axial passageway in the piston rod to said ring and a
lubricant-impregnated material in the passageways in said rod and
piston.
Description
This invention relates to fluid cylinders, and, more specifically,
to means for lubricating piston-cylinder units of the type operated
by gas under pressure in a closed fluid system.
In metal die forming operations it is common practice to yieldably
restrain movement of the die members by means of fluid springs.
Frequently such fluid springs comprise piston-cylinder units
connected to a reservoir of gas under pressure, such as nitrogen.
With such closed pressure systems the gas itself does not contain a
lubricant, as is the case with systems wherein piston-cylinder
units are operated by pressurized air supplied by a compressor and
the air lines are equipped with lubricators. Thus, in closed type
systems of the type to which the present invention relates, in
order to reduce wear and minimize service problems auxiliary means
are provided to lubricate the surfaces of the cylinder, piston and
piston rod which are in sliding contact.
The present invention has for its primary object the provision of a
novel lubricating arrangement for such piston-cylinder units
operated by non-lubricated gas under pressure.
More specifically, the present invention contemplates the provision
of an air passageway to the cylinder chamber on the side of the
piston opposite that to which gas under pressure is supplied and a
lubricant-impregnated material in said passageway through which the
air flows. When the piston moves in the cylinder in a direction
tending to create a negative pressure in said cylinder chamber, air
is drawn through the passageway and lubricant becomes entrained
therein so that the air/lubricant mixture flowing into the cylinder
provides adequate lubrication for the surfaces of the piston,
piston rod and cylinder which are in sliding contact. The
arrangement of this invention also contemplates a means for
prolonging the supply of lubricant to a lubricant-impregnated
piston ring, such as is conventionally employed in such
cylinders.
Other objects and features of the present invention will become
apparent from the following description and accompanying drawings,
in which:
FIG. 1 is a fragmentary vertical sectional view of a fluid cylinder
according to the present invention taken along the line 1--1 in
FIG. 2 and illustrating the manner in which it is utilized in a die
assembly;
FIG. 2 is a top view of the cylinder shown in FIG. 1;
FIG. 3 is a sectional view along the line 3--3 in FIG. 1;
FIG. 4 is a perspective view of the disc utilized in the check
valves employed in the cylinder;
FIG. 5 is a fragmentary sectional view illustrating on an enlarged
scale a portion of the arrangement shown in FIG. 1;
FIG. 6 is a fragmentary sectional view taken along the line 6--6 in
FIG. 2;
FIG. 7 is a fragmentary view, with parts broken away, of the
cylinder cap as viewed from the under side thereof; and
FIG. 8 is a sectional view along the line 8--8 in FIG. 1.
Referring to FIG. 1, there is illustrated a fluid spring generally
designated 10 in the form of a piston-cylinder unit according to
the present invention which is arranged between a vertically
movable die member 12 and a fixed support 14, which in the
illustrated arrangement comprises a manifold plate. The overall
arrangement shown in FIG. 1 is generally similar to that
illustrated in my copending application Ser. No. 536,084 and now
U.S. Pat. No. 3,947,005. The piston-cylinder unit 10 comprises a
cylinder 16 which is mounted as by axially spaced rubber rings 18
in an outer cylindrical sleeve 20. Cylinder 16 is secured in sleeve
20 by means of a threaded clamping ring 22 which urges a metal
washer 24 downwardly against the upper rubber ring 18. The two
rings 18 are separated by a flange 26 on cylinder 16 and the lower
ring 18 is seated on a radially inwardly extending shoulder 28 on
sleeve 20. Sleeve 20 is threaded, as at 30, into a bore 32 formed
in manifold plate 14. A passageway 34 connects bore 32 and thus the
lower opened end 36 of cylinder 16 with a reservoir 38 containing a
gas (such as nitrogen) under a predetermined high pressure. The
arrangement of cylinder 16 in sleeve 20 permits the cylinder to
tilt slightly relative to the central vertical axis of sleeve 20 in
the event that the direction of movement of die member 12 is
slightly inclined to the central axis of cylinder 16. This general
arrangement is completely described in my aforesaid copending
application.
Within cylinder 16 there is arranged a piston 40 to which a rod 42
is fixedly connected. Rod 42 extends upwardly through a cylinder
cap 44. Piston 40 divides the interior of the cylinder into a
pressure chamber 46 and an atmosphere or idle chamber 48. Piston 40
is sealed in cylinder 16 by means of a conventional annular seal 50
formed of an elastomer. The piston is also provided with a fiber
wear ring 52 and a lubricant-impregnated felt ring 54.
Cap 44 is preferably formed of a metal (such as aluminum) which is
a good conductor of heat. It is secured to the upper end of
cylinder 16 as by a plurality of screws 56 (FIG. 6). Around its
periphery and on the top side thereof cap 44 is formed with a
plurality of fins such as indicated at 58. Fins 58 assist in
maintaining the piston-cylinder unit at a desired low operating
temperature. It will be observed that cap 44 extends radially
outwardly beyond and overhangs the upper end of cylinder 16. The
lower end of cap 44 is centrally bored as at 60 so as to be
telescopically received over the upper end of cylinder 16. The
upper portion of bore 60 is radially enlarged as at 62 to define an
annular passageway 64 between the outer periphery of cylinder 16
and the inner periphery of cap 44.
As is illustrated in FIGS. 1 and 5, passageway 64 is of generally
rectangular cross section. A plurality of radial openings 66 in cap
44 establish communication between annular passageway 64 and the
surrounding atmosphere. Openings 66 are located between a pair of
adjacent fins 58 so as to be generally shielded from oil, dirt and
other foreign matter which is usually present around dies. Within
passageway 64 there is arranged a member 68 which is impregnated
with a lubricant such as oil. Member 68 preferably comprises a
fibrous material (such as felt or the like) enclosed within a
screen cloth mesh. It will be noted that annular member 68 has a
vertical dimension substantially less than that of passageway 64.
Furthermore, as shown in FIG. 3, the oil-impregnated member 68 does
not extend completely around passageway 64; its opposed ends are
spaced apart circumferentially to provide an air space 70
therebetween which is in communication with one of the radial
openings 66.
Within the upper end of cylinder 16 there is arranged an inlet
valve 72 and an outlet valve 74. These valves are unidirectional
check valves and are oppositely oriented so that valve 72 only
permits the ingress of air to chamber 48 and valve 74 only permits
the egress of air from chamber 48. Each of these valves are of
similar construction and include a light-weight movable valve disc
76 of cruciform shape. A disc 76 is located at the lower end of
valve 72 and a similar disc 76 is located at the upper end of valve
74. Discs 76 or equivalent members are employed for unidirectional
air flow through the valves in the manner of a conventional check
valve. A clearance space 78 is machined on the underside of cap 44
adjacent inlet valve 72 so that the air in annular passageway 64
above the lubricant-impregnated member can flow into chamber 48
through valve 72. An opening 80 in cap 44 registers axially with
the central passageway of valve 74 to permit the exhaust of air
from chamber 48. The free end of piston rod 42 is guided in the
cylinder by a nylon bushing 82 formed with a wiper sealing lip 84
at its upper end. In the arrangement illustrated, if desired,
exhaust check valve 74 may be omitted and air permitted to escape
from chamber 48 through an axial groove 86 in bushing 82 (FIG.
3).
Piston 40 and piston rod 42 are formed with a central axially
extending bore 88 which is threaded at the free end of the piston
rod and closed by a plug 90. Bore 88 extends downwardly to at least
the plane of the felt wiper ring 54 and communicates with the
annular groove in which ring 54 is seated by means of a pair of
radially extending passageways 92 (FIGS. 1 and 8). Bore 88 and
radial passageways 92 are filled with an oil-impregnated fibrous
wick material 94.
The operation of the arrangement illustrated is clear. As shown,
the free end of piston rod 42 abuts the bottom face of die member
12 and is urged upwardly thereagainst by reason of the gaseous
pressure in chamber 46 which is connected by passageway 34 with
reservoir 38. As die member 12 descends it causes piston 40 to move
downwardly in cylinder 16, thus increasing the pressure in chamber
46 and tending to evacuate chamber 48. The tendency to create a
negative pressure in chamber 48 causes air to be drawn into
passageway 64 through openings 66. The bulk of this air will flow
upwardly through the oil-impregnated member 68 and around
passageway 64 to inlet check valve 72. Since the pressure in
chamber 48 is less than in passageway 64, disc 76 assumes the
position illustrated in FIGS. 1 and 5 to allow air from passageway
64 to flow through valve 72 and into chamber 48. As this air flows
upwardly through member 68 oil is entrained therein and flows into
chamber 48 along with the air. The oil entrained in the air thus
lubricates and reduces wear on piston rod 42, the inner wall of
cylinder 16 and the bore of bushing 82. In turn this will assure
concentricity of the piston and piston rod within the cylinder.
As die member 12 moves upwardly the pressure of the gas in chamber
46 causes piston 40 to move upwardly, thus ensmalling chamber 48
and causing the air to be discharged therefrom through exhaust
valve 74. Since at this time the pressure in chamber 48 is greater
than atmospheric, valve disc 76 of valve 72 is urged upwardly to
block the passageway in valve 72 and the valve disc 76 of valve 74
is urged upwardly to permit the escape of air from chamber 48. As
pointed out previously, if desired, the air exhaust passageway from
chamber 48 may be provided simply by the shallow groove 86 in
bushing 82. In this event the sealing lip 84 at the upper end of
bushing 82 will serve to prevent the ingress of a substantial
amount of air to chamber 48 through passageway 86 when piston 40
descends in the cylinder.
The air gap 70 illustrated in FIG. 3 (which is defined by the space
between the ends of member 68) is provided as a precautionary
measure to assure the free flow of air into chamber 48 in the event
that the oil-impregnated member 68 should become clogged. However,
it will be noted that the provision of cap 44 and the location of
passageway 64 and the inlet openings 66 are designed to prevent
oil, dirt, grease and other foreign matter which are invariably
present around dies from being drawn into passageway 64. It will
also be apparent from the foregoing description that the
oil-impregnated wick member 94 provides a prolonged supply of oil
to the felt ring 54 which eliminates the necessity of frequent
servicing and replacement of ring 54. However, servicing of
cylinder 16 is relatively simply since the valves and the
oil-impregnated member 68 are readily accessible by loosening
screws 56 and removing cap 44 from the upper end of the
cylinder.
* * * * *